What is leaking from my carb, should I be concerned?

[estcstm3]

Hi all,

The bike is running pretty good. I was looking under my carbs and noticed really on the left hand side (alternator side), that it looks like maybe an oil,fuel mixture is dripping from the bottom of the carb. I am slowing learning how to work on my bike and have really just messed with valves, camchain, oil change, so I am not very versed in my carbs yet.

Should I be concerned? Any advice on whats going on?

let me know if you can see the pics



I have a 1975 xs650b.

 

[nj1639]

Looks like some kind of chain oiler is running from the breather down through the left side engine cover. Interesting......might be leaking out at the upper end of that hose and dripping down.

 

[estcstm3]

here are the same pics but I rotated them correctly hopefully its easier to visualize.

 

[pamcopete]

If you have the stock air filters, then the crankcase breather vents to the air filter box. That is probably engine oil from the crankcase breather. If it is excessive, then you could have excessive blow-by or just too much oil in the crankcase. Check compression and the oil level.

There was a service bulletin from Yamaha a few years ago about the dip stick not being marked corrected, so it is possible that the crankcase is overfilled if the mod to the dipstick was not done.

It's difficult to read that image, but basically what it is saying is that max oil level is midway between the max and min markings, or about a 10mm lower oil level.

The best way to check to see if this bulletin applies to you is to check where the oil level is after an oil change when you have added the two quarts.

 

[weekendrider]

Are we sure it(the crankcase) vents to the air boxes?
If so splain ta me what that hose is going into the left side cover. The one right next to the clutch cable.
That stain looks green to me. And I'm betting it ain't anti-freeze or an exotic oil.
But the bike isn't here and I'm not there.

 

[pamcopete]

weekend...,

Like you say, I'm not there and the bikes not here...Just offering a suggestion that I had experienced in my trusty '78 as it got a little older and had excessive blow by.

 

[weekendrider]

Pete it could very well be excessive blow by. And with it dumping under the side cover who is to say where the wind might take it. But the green color except where it has gathered around the case bolt and is turning shellac brown suggests old fuel to me. The float height is set right to the top and you lean the bike to the side maybe some is spilling out the left overflow?

 

[pamcopete]

weekendrider,

Well, except that old fuel would evaporate and leave a trace. This still looks fresh to me, but it could be both oil mixed with some fuel.

 

[estcstm3]

Hi All,

Im as stumped as you all are. I believe I have the revised dipstick but how do I tell? Also do I measure from the dipstick fully screwed in?

The breather tube into the top of the alternator case is pretty dry, the "oil" seems to be coming from that plastic piece at the bottom of carb. That liquid is only on the that left hand side the right hand side is perfectly dry. I dont have a compression gauge.

Any basic things I should be doing? My sparkplugs are pretty black (i have a question about those in another thread).

Oh yeah and I have pod filters on the bike, not the oem airbox.

 

[Brian902]

" I believe I have the revised dipstick but how do I tell?"

Question did you actually read Post # 4?

 

[nj1639]

I rest the dipstick in, unscrewed, and make sure the level is halfway between the two marks......'course you could then screw it all the way in and then check and see where the level is......

 

[gggGary]

Lets say that's a slow gas leak, though it does look a bit thick and the stain is kinda concentrated gas tends to spread out. If the covers are waxed that may explain the narrow trail.
When was the last time the carbs were gone through?
Assuming it's gas;
If you have a leaky petcock, the low carb will tend to overflow.
A poorly sealing float valve will show as a carb overflow.
A cracked sinking float will show as a rich plug and carb overflow.
Dirt or rust in fuel will tend to cause a float valve to leak ditto.
A float set to high will show as........

So what you will need to do is eliminate the above as possible problems.

As an experiment put it on the center stand, clean off the gas stain, what do you see a day or three later?

PS the crank vent exiting to a hole above the chain is correct for a 75

 

[Royboy]

My 78' SE produces a similar mess if I ride 50 miles or more and just pull in and shut her off. In the morning I'll find the bottom of each carb has a drop of fuel/oily residue just about ready to drip off. Clean it off with a paper towel and it won't reappear until the next ride. I also notice a bit of blow back on both side covers. It smells like fuel. At first I thought the float bowl gaskets were leaking but that wouldn't stop when it was parked. I'm pretty much convinced it's blow by from the crankcase vent and am going to try the brake booster valve trick to see if that will cure it. I'll let you know.

roy

 

[gggGary]

Mis information deleted... oil level is checked with the bike on the center stand. My bad... a 650 v star's oil is checked with the bike on the wheels (it has no center stand).
Wipe the drip off with your finger and smell. Wait a bit, rub it between two fingers, oily?

drive chain tension is checked with the bike upright sitting on the suspension (tires)

 

[estcstm3]

" I believe I have the revised dipstick but how do I tell?"

Question did you actually read Post # 4?

Yes just noticed Pete's tip About putting in 2 Quarts to check. Thanks.

 

[estcstm3]

Not often mentioned; oil level (and chain tension) is checked with the bike upright sitting on the suspension, NOT on the center stand.
Wipe the drip off with your finger and smell. Wait a bit, rub it between two fingers, oily?

Did not know this is just did my cam chain on center stand. But the leak was before then. The carbs were overhauled about a year ago by another member on this board who I bought the bike off of. I. Have not touched the carbs. Down here in fl I have easy access the ethanol free gas which is all i run in it. My plugs are pretty black. When I'm back home I'll text out the oil by rubbing it. It did go from ny to fl but it was not really in the mt or anything.

 

[5twins]

I'm thinking you have a slow fuel leak from that left float bowl, either from the drain plug or the plastic overflow nipple. It's dark colored and not clear like fresh fuel because it's mostly evaporating before it builds up enough to drip. The clear portion of the fuel is evaporating away and leaving behind the residue and additives. The same thing occurs inside your carb if it sits a long, long time with fuel in it. You're left with the fuel gum and varnish. You might try sanding the copper washer on the drain bolt smooth on both sides, removing any grooves and irregularities, on some 400 or 600 paper. If it's the plastic nipple, I'm not sure what to do. It fits over a metal fitting pressed into the bowl. Your carbs are so old, maybe that's come loose.

 

[gggGary]

Sorry cam chain on the center stand is fine. Adjust drive chain on the wheels, just a random tidbit...

Is that drip happening when it's being ridden or when it's sitting??

 

[pamcopete]

If you have a leaky petcock, the low carb will tend to overflow.

I think this is a misconception. The carbs will only overflow if the floats are not set properly or if the float needle is worn out. A leaky pet cock will cause a strong odor of gasoline in an enclosed space, such as a garage, because the leak replenishes the aromatics (as in aroma) as they evaporate as the aromatics are the first component of gasoline to evaporate. If everything is tight, then once the aromatics evaporate, there is no more so the evaporation of the rest of the components is slower and not as aromatic.

I also turn on the petcock (to prime position) if the bike has been sitting for awhile in order to replenish the aromatics because without the aromatic component, the gasoline in the bowl is really not gasoline. I also move the bike back and forth and side to side in order to mix the aromatics in with whatever is in the bowls. Starts are much better this way.

 

[pamcopete]

Not often mentioned; oil level (and chain tension) is checked with the bike upright sitting on the suspension, NOT on the center stand.
Wipe the drip off with your finger and smell. Wait a bit, rub it between two fingers, oily?

I actually have a rare owners manual for my XS650/H and you are correct about the chain, but not the oil. On page 42 of the official owners manual it says to "Place the motorcycle on the center stand" However, it is rather ambiguous when it says when using the dip stick to check the oil level, "The oil level should be between the min and max levels as marked on the dip stick." This is not helpful when checking the oil after an oil change.

I check the oil level after an oil change when I have put 2 qts. in the crankcase. The book calls for 2.1 Qts, but I have found that the extra .1 qt, blows out the vent after a few miles anyway, so 2 qts is more practical. I also screw the dip stick all the way in to get a reading, which shows at the full mark because I only used 2 qts instead of 2.1.

I have three Hondas in the garage as well, and Honda is a little more practical because you can check both the oil level and the chain slack with the bike on the centerstand. This makes it a lot easier to find the tight stretch in the chain, which you are supposed to use when adjusting the chain slack. Yamaha also wants you to find the tight section of chain, but with the wheel on the ground, so over the years I have figured out what the chain tension should be with the bike on the center stand.